U.S. patent number 5,068,793 [Application Number 07/276,319] was granted by the patent office on 1991-11-26 for apparatus for triggering passenger protection systems.
This patent grant is currently assigned to Robert Bosch GmbH. Invention is credited to Claus Condne, Bernhard Mattes, Dieter Schmalz.
United States Patent |
5,068,793 |
Condne , et al. |
November 26, 1991 |
Apparatus for triggering passenger protection systems
Abstract
The invention is directed to an apparatus for triggering
passenger protection systems particularly restraining systems in
vehicles during their impact. In the previous systems, there is the
disadvantage that the protective systems are only triggered late or
not at all during critical impact situations at relatively low
negative accelerations. The disadvantage chiefly results because a
differential signal is fed to the input of an integrator which
comprises the difference between a signal derived from the
acceleration and a constant threshold value signal. According to
the invention, a variable threshold value is deducted from the
derived acceleration signal rather than a constant threshold
value.
Inventors: |
Condne; Claus (Wadgassen,
DE), Mattes; Bernhard (Sachsenheim, DE),
Schmalz; Dieter (Pleidelsheim, DE) |
Assignee: |
Robert Bosch GmbH (Stuttgart,
DE)
|
Family
ID: |
6303838 |
Appl.
No.: |
07/276,319 |
Filed: |
October 6, 1988 |
PCT
Filed: |
February 28, 1987 |
PCT No.: |
PCT/DE87/00078 |
371
Date: |
October 06, 1988 |
102(e)
Date: |
October 06, 1988 |
PCT
Pub. No.: |
WO88/00146 |
PCT
Pub. Date: |
January 14, 1988 |
Foreign Application Priority Data
|
|
|
|
|
Jun 27, 1986 [DE] |
|
|
3621580 |
|
Current U.S.
Class: |
701/46; 280/735;
180/271 |
Current CPC
Class: |
B60R
21/16 (20130101); B60R 21/0133 (20141201); B60R
21/0132 (20130101) |
Current International
Class: |
B60R
21/01 (20060101); B60R 021/32 () |
Field of
Search: |
;280/801,735,748
;180/282,268,271,282 ;364/424.01,424.05 ;340/669 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Chin; Gary
Attorney, Agent or Firm: Striker; Michael J.
Claims
What is claimed as new and desired to be protected by Letters
Patent is set forth in the appended claims.
1. An apparatus for triggering passenger protection system, in
particular restraining system of motor vehicle upon impact, said
apparatus comprising an acceleration receiver for outputting an
acceleration signal in response to a vehicle acceleration;
differential means having a first input for receiving the
acceleration signal, a second input for receiving an integration
threshold value signal, and an output for outputting a differential
signal; an integrator having an input for receiving the
differential signal and an output for outputting a control signal
upon receiving the differential signal; a threshold value
transmitter for communicating a variable integration threshold
value signal to said second input of said differentiation means in
response to the control signal; the control signal causing
triggering of said protection system when the control signal
exceeds a predetermined triggering value.
2. An apparatus according to claim 1, wherein said differential
means, said integrator, and said threshold value transmitter form a
unit representing a low-pass filter in which said first input of
said differential means represents an input of said low pass filter
and said output of said integrator represents an output of said
low-pass filter.
3. An apparatus according to claim 1, comprising means for
outputting a triggering signal for triggering the protection system
in response to the control signal exceeding the predetermined
triggering value, said triggering signal outputting means including
a triggering threshold switch connected with said integrator for
receiving the control signal and outputting said triggering signal
and an output amplifier connected with said triggering threshold
switch for amplifying said triggering signal, said triggering
threshold switch having an output which is blocked for an input
signal lying below the predetermined triggering threshold
value.
4. An apparatus according to claim 1, comprising means for
increasing the integration threshold value as the control signal
from the integrator increases and for decreasing the integration
threshold value as the output signal of the integrator
decreases.
5. An apparatus according to claim 1, comprising means for
continuously increasing the integration threshold value as the
control signal from the integrator increases.
6. An apparatus according to claim 1, comprising means for
increasing in steps the integration threshold value as the control
signal from the integrator increases.
7. An apparatus according to claim 1, comprising means for enabling
the integration threshold value to follow the control signal from
the integrator in a linear manner.
Description
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for triggering
passenger protection systems, particularly restraining systems in
vehicles on at impact. Such systems are known e.g. from the DE-PS
26 12 215. The triggering of such systems at the appropriate point
in time presents certain difficulties. On one hand, because the
rapidity of the sequences of movement, the sensitivity of the
sensor must be great enough so that, e.g. during an impact at 50
km/hour, the registering of the impact, as well as the safety
measure itself, such as tightening of the straps or blowing up of
cushions, must be completed within 40 ms. On the other hand,
triggering may not be effected for obvious reasons when criteria
which only resemble an impact are present at the sensor, as can
occur, for example, when driving over an obstacle or even during
normal braking of the vehicle. Moreover, it must be taken into
account that below an acceleration of approximately--4g the
passengers can support themselves without additional restraining
measures, i.e. the triggering of safety device can result in
increased risk in this event, resulting in the opposite of the
intended purpose. It has been shown that a dangerous impact
situation is characterized above all in that the polarity of the
acceleration does not change over a distinctly longer period of
time in contrast to intensive short-term accelerations, as occur
e.g. when driving over a curb or also as a result of a blow by a
hammer. The acceleration changes repeatedly within a very short
period of time.
In order to separate critical impact situations from uncritical
impact situations in an improved manner, it is known, e.g. from the
US-PS 37 01 903, to provide an amplitude limiter, an integrator,
and a threshold circuit in addition to the acceleration receiver.
It is the object of the amplitude limiter to limit upwardly the
amplitude of an impact, so that the following integrator reaches
the threshold voltage of the threshold value switch, which is
connected downstream, only during impacts at intense, more
sustained accelerations. If the amplitude of impacts is too small,
i.e. if it lies below the level fixed by the amplitude limiter, no
output signal appears at the input of the integrator. In addition,
the integrator causes the triggering voltage for the threshold
value switch connected downstream to be reached only after the
expiration of a predetermined period of time.
A disadvantage of the previously known systems consists in that
they do not trigger or trigger late at low accelerations such as
occur e.g. during oblique impact.
Instead of using an amplitude limiter, it is further suggested to
deduct a constant value from the output value of the acceleration
receiver. Since the integrator is adjusted in such a way that it is
not capable of transmitting a negative output signal, output
signals of the acceleration receiver lying below the threshold
voltage have no effect on the output of the integrator.
European patent application EP-A-O 156,930 discloses an apparatus
for triggering a restraining system of a motor vehicle upon impact
in which an output signal from an acceleration receiver is
communicated to an integrator the output signal of which actuates
the restraining system as soon as the integrator output signal
exceeds the triggering threshold value. A variable integration
threshold value is applied to the integrator, and a reference value
of the integrator is shifted as a result of the differentiation of
the output signal of the threshold value switch. First, the
integration threshold value is changed in accordance with a change
in the triggering threshold value in order to insure a reliable
response and a reliable triggering of the restraining system in
response to short input impulses. However, this triggering system
does not permit to obtain an early reliable triggering of the
passenger protection system at comparatively low acceleration
values which occur at an oblique impact.
The aforementioned systems do indeed solve the problem of only
registering accelerations which lie above a determined level and a
determined time period. But it is a disadvantage in these systems
that they do not trigger or trigger late at low accelerations such
as occur during an oblique impact, since, due to the deduction of a
constant value from the measured acceleration signal, the
acceleration value remaining to be integrated leads too late or not
at all to an integration value which exceeds the triggering
threshold of the system connected downstream of the integrator.
Therefore, the present invention is based on an apparatus for
triggering passenger protection systems, particularly restraining
systems, in vehicles during impact, in which the output signal of
an acceleration receiver which is reduced by an amount
corresponding to an integration threshold value, or a signal
derived from this output signal, is integrated in an integrator,
wherein the output signal of the integrator triggers the passenger
protection system, possibly via an output stage, as soon as the
integrator output signal exceeds a triggering threshold value.
It is the object of the invention to provide measures in such an
apparatus which ensure a prompt, secure triggering of the passenger
protection system during critical impact processes at comparatively
low acceleration values.
SUMMARY OF THE INVENTION
The object of the invention is met, according to the invention, by
forming the integration threshold value to be deducted from the
measured acceleration signal or from a signal derived from the
latter as a variable value. In principle, the invention also
consists in that a constant value is no longer deducted from the
acceleration value but, rather, the threshold value to be deducted
is made to be dependent on the respective situation. This measure
makes it possible to overcome the disadvantage that the residual
value remaining to be integrated after the deduction of a constant
threshold value is very small so that the integration can take a
rather long time before the system is finally triggered. At such
low acceleration values, it is suggested, rather, to keep the
threshold value which is to be deducted extremely small or to set
it to zero so that a triggering can be implemented more
quickly.
In a further development of the invention, it is suggested to
change the integration threshold value as a function of the output
signal of the integrator. The automatic adjustment of the threshold
value can be handled relatively simply by means of this. It is
particularly recommended, in a further development of the
invention, that the integration threshold value increases as the
output signal of the integrator increases, and vice versa, i.e.
when the output value of the integrator is low, the threshold to be
deducted is also low. Accordingly, a relatively steep rise of the
output signal of the integrator is obtained in the initial phase
also at relatively low measured acceleration values, since it is
not necessary to wait first until a constant threshold voltage is
exceeded with regard to integration. The dependence of the
integration threshold value on the output signal of the integrator
can run continuously, but can also run in stages in a stepwise
manner. Other dependencies are also conceivable.
A particularly simple control of the integration threshold value is
obtained when this value follows the output signal of the
integrator in a linear manner, wherein there are other suitable
possibilities of change with respect to the time lag between the
two synchronous signals.
The output signal of the integrator may be fed back indirectly to
the input of the integrator via a threshold value transmitter which
forms this output signal. A differential element is connected prior
to the input of the integrator which deducts the fed-back threshold
value from the measured acceleration signal or from a signal
derived from this acceleration signal. This threshold value
transmitter can feed the integrator output signal back to the input
of the integrator with a time delay, but can also more or less
distort the integrator output signal. In the event that the time
delay is relatively slight and the transmitted threshold value is a
reflection of the integrator output signal, an e-function results
substantially for the output signal of the integrator, since the
value to be deducted from the acceleration input signal becomes
increasingly larger until the two values are finally identical to
one another and the input value of the integrator changes to zero.
However, if a constant value is deducted from the measured
acceleration signal, as was suggested, an integration first
commences at that moment when the input signal exceeds the constant
threshold value. If the acceleration value rises very quickly, the
integration signal also rises very quickly. But if the acceleration
is relatively low, the differential value to be integrated can
remain quite low and the threshold value at the output of the
integrator necessary for triggering can accordingly only be reached
quite late.
It is recommended that the apparatus, according to the invention,
be constituted by electronic components. In so doing, it is not
absolutely necessary to effect the resulting control loop by means
of returning the output signal of the integrator to its input,
rather, the resulting low-pass behavior can also be simulated by
means of a differently constructed, preferably electronic circuit
with low-pass behavior.
BRIEF DESCRIPTION OF THE DRAWINGS
Additional features and advantages of the present invention will be
better understood from the description that follow with reference
to appended drawings wherein:
FIG. 1 shows a block-diagram of a prior art an apparatus.
FIG. 2 shows a block-diagram of an apparatus according to the
invention,
FIG. 3 shows the curve of the acceleration during a critical
impact,
FIG. 4 shows a signal derived from the acceleration, which signal
is fed to the integrator input, and
FIG. 5 shows the output signal of the integrator.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 shows an apparatus, such as has already been suggested, upon
which the invention is based. An acceleration signal be is returned
to an acceleration receiver B which transmits a corresponding
electrical signal ba to a first input D1 of a differential element
D. A constant threshold value is fed to a second input D2 of the
differential element D, which threshold value is deducted in the
differential element D from the output signal ba of the
acceleration receiver B. The differential of the two signals at D1
and D2 forms the input signal ie of the integrator I. As soon as
the output signal ia of the integrator I exceeds a determined
threshold value, a triggering threshold switch A switches through,
the output signal aa of the latter actuating the passenger
protection system via an amplifier. In practice, the output signal
aa of the triggering threshold switch A can be amplified by the
amplifier E and possibly transformed, wherein the output signal ea
of the amplifier E then actuates an ignition device which serves to
tighten a strap or blow up an air bag. A disadvantage in the system
described above is that the input signal ie can become quite small
when the difference between D1 and D2 is small. The threshold value
aV determined by the triggering threshold switch A is accordingly
only exceeded very late by ia, wherein A releases a triggering
signal aa at the output of A. Such problems occur particularly when
driving into a vehicle traveling in front or during an oblique
impact, that is, in cases in which there is a critical impact but
the occurring change in velocity is not that high.
FIG. 3 shows a typical curve of the acceleration. It is assumed
that the output signal of the acceleration receiver B fed to the
differential element D takes a similar course as be (see FIG. 4).
As can be seen from FIG. 4, a constant threshold value--4g, which
is transmitted by a threshold value transmitter S and fed to the
second input D2 of the differential element D, is deducted from ba
via the differential element D.
Thus, only the parts of the signal ba lying below the--4g--line
participate in a change of the integration signal ia having a
course in the positive direction. Circuit measures ensure that ia
cannot be negative. In FIG. 5, the course of the signal ia at the
output of the integrator I as a function of t is shown as a curve
drawn in dashes. At time t1, ba falls below the threshold
value--4g, so that ie is greater than zero and the adding
commences. At time t5, the integration value ia increases the most,
while, at the following time t2, the integration value ia reaches
its highest value. Next, ba falls below--4g and ia decreases
accordingly until, taken by itself, it would have to pass into the
negative area, but this is prevented by measures relating to
circuit technology. At time t3, ba again falls below the--4g line,
so that ia again adopts positive values which decrease again after
t4, since ba exceeds the 4g line again after this point in
time.
As can be seen from FIG. 5, it is to be established, as a result,
that the threshold value .DELTA.V of the triggering threshold
switch, according to FIG. 5, is not reached and accordingly the
passenger protection system Z is not triggered, although b
repeatedly falls below the threshold value--4g.
FIG. 2 shows the construction, according to the invention, of the
apparatus according to FIG. 1. The substantial difference between
FIGS. 2 and 1 consists in that the output signal ia of the
integrator I is returned to the differential element D via a
threshold value transmitter S, so that a threshold value, which is
variable with respect to time and is controlled by ai, is present
at the second input D2 of the differential element D, which
threshold value is deducted from the output signal ha.
Investigations have shown that a response behavior of the passenger
protection system which is much more favorable than that of the
construction according to FIG. 1 can be achieved by means of such a
configuration. In particular, the reason for this is that, at
smaller negative acceleration values, the full value of ha is also
integrated as long as ia is still negligibly small, so that ia
approximates the threshold value .DELTA.V much more quickly than in
the construction according to FIG. 1. In addition, the construction
according to FIG. 2 is modified relative to the construction
according to FIG. 1 to the extent that ia can also achieve negative
values. This is important in the event that an impact from the rear
results in an impact from the front, for example, in that a vehicle
following the secured vehicle pushes the latter against a
stationary line of vehicles. In these cases, no threshold value is
deducted from the value ha, which is then positive, rather, a
threshold value sa with reversed polarity is added, so that an
accelerated integration also occurs in this case in the direction
of the threshold value .DELTA.V when the acceleration direction
changes. The shape of the solid curve ia prior to time t0 is
characteristic of such a behavior. As can be seen, in addition,
from FIG. 5, the rise of ia in the circuit arrangement, according
to the invention (see solid line in FIG. 5), already commences at
time to instead of at time t1 according to the example according to
FIG. 1. According to the invention, the threshold value sa follows
the signal ia, wherein ha is equally as large as sa at time t6, so
that the integration signal has reached a first maximum value.
After this, the threshold value signal sa prevails over the
modified acceleration signal ha because of the time delay or a
corresponding adjustment of the threshold value transmitter S, so
that the integration value ia decreases again. The threshold value
sa, which drops again later because of the falling value of ai,
leads, in connection with an output signal ha which increases
again, to a rise of the integration signal until the latter finally
exceeds the threshold value .DELTA.V and accordingly triggers the
passenger protection system Z.
Another important change in the circuit arrangement according to
FIG. 2, as opposed to FIG. 1, consists in the use of a high-pass
filter H which is connected between the acceleration receiver B and
the differential element D. This high-pass filter suppresses slow
changes in accelerations, e.g. acceleration changes with a
frequency below 1 Hz. This step serves, above all else, to suppress
more or less sharp braking or acceleration processes which occur
during the normal operation of the vehicle, but are uncritical and
should not lead to a triggering of the protective system. In the
same way, slow changes in the output signal ba due to temperature
behavior of the acceleration receiver B can be suppressed by means
of the high-pass filter.
If the behavior of the circuit according to FIG. 2, according to
the invention, is evaluated mathematically in the sense of control
technology, the following function results: i.sub.1 =.intg.(h.sub.a
-c.multidot.i.sub.a) dt, wherein c forms a constant. With the use
of the Laplace transform, it follows: p.multidot.i.sub.a =h.sub.a
-i.sub.a .multidot.c. This gives the transfer function ##EQU1##
This is the transfer function of a low-pass filter, so that, very
generally, an electrical low-pass filter can be used for the
control loop which fulfills the first above-named mathematical
function. However, it is not necessary for this low-pass filter to
have the construction of the low-pass filter TP shown by means of
the dashed border in FIG. 2, rather, very generally, a preferably
electrically or electronically operating circuit with the behavior
of a low-pass filter can be selected in order to achieve the
advantages according to the invention. However, a low-pass filter
function can be achieved at considerably less expense than the
low-pass filter TP shown in FIG. 2.
The advantage of the invention accordingly consists in that
relatively small acceleration signals can already be integrated by
means of the integrator. The delayed increase of the threshold
value s.sub.a ensures that the output signal of the integrator
i.sub.a does not reach the triggering threshold .DELTA.V during
impact at speeds which are too low, e.g. during front end impacts
at speeds less than 15 km/h. Since an ia-signal is already present
at low accelerations because of the absent constant threshold
value, the triggering threshold is reached more quickly as the
acceleration signal rises. The restraining device is accordingly
activated sooner and an improved protective action is achieved
particularly during oblique impacts of vehicles having a less rigid
front part (lightweight construction). The acceleration receiver B
detects delays as well as accelerations. This is important for
correctly evaluating hammer blows and speed changes of the vehicle
during the impact, since the vehicle regularly exhibits an
oscillating behavior during the impact and since, in addition, a
frontal impact is frequently preceded by a shock in the rear of the
vehicle. It must also be taken into account that relatively slight
delays and accelerations occur during normal operation of the
vehicle (in the order of magnitude of .ltoreq.1.0 g) which have no
effect on the ia-signal. Therefore, this signal is independent from
the starting speed of the vehicle, also, additionally, by means of
the manner of functioning of the high-pass filter H. The only
influencing variable is the acceleration curve during at impact, so
that the engine acceleration or the customary braking have no
influence on the triggering of the safety system.
It will be understood that each of the elements described above, or
two or more together, may also find a useful application in other
types of constructions differing from the types described
above.
While the invention has been illustrated and described as embodied
in an apparatus for triggering passenger safety protection systems,
it is not intended to be limited to the details shown, since
various modifications and structural changes may be made without
departing in any way from the spirit of the present invention.
Without further analysis, the foregoing will so fully reveal the
gist of the present invention that others can, by applying current
knowledge, readily adapt it for various applications without
omitting features that, from the standpoint of prior art, fairly
constitute essential characteristics of the generic or specific
aspects of this invention.
* * * * *